1. Field of the Invention
The present invention relates to a device for detecting a position of a moving body which device is used in a power window device, which moves a window glass of a vehicle door to open and close the window glass, or is used in a sunroof device, which moves a sunroof to open and close the sunroof, or the like.
2. Description of the Related Art
A motor is used as the drive source in a power window device, which moves a window glass of a vehicle down and up to open and close the window glass, or in a sunroof device, which moves a sunroof to open and close the sunroof.
There are power window devices which have a so-called catch-preventing function which prevents a portion of the body of a vehicle occupant or a foreign object from being inadvertently caught between the window glass and the window frame of the vehicle door. The following two types of structures are examples of power window devices equipped with such a catch-preventing function. (1) A limit switch is disposed at a predetermined position of the door. On the basis of signals from the limit switch and the lock current of the motor, a determination is made as to whether a foreign object has been caught by the window glass, and the movement of the window glass, i.e., the rotational position of the motor, is controlled appropriately. (2) The rotational frequency of the armature is detected by providing a Hall IC or a special commutator. On the basis of the rotational frequency detection signal (the number of pulses or the pulse width of the pulse signal), a determination is made as to whether a foreign object has been caught, and the rotational position of the motor is controlled appropriately.
However, in such power window devices (motor rotational position detecting mechanisms), a drawback arises in that complicated adjustment of the installation positions while the motor and the window regulator and the like are being installed or complex resetting after installation is needed. Further, in cases in which a catch-preventing mechanism is used, there is a drawback in that parts such as a control device or the like are expensive and are imprecise.
The inventors of the invention disclosed in the present application have proposed devices for detecting a position of a moving body in order to overcome the aforementioned drawbacks (e.g., Japanese Patent Application Laid-Open (JP-A) No. 8-29114).
This device for detecting a position of a moving body includes a planetary gear group, a switch portion and a clutch mechanism. The planetary gear group is formed by a ring gear rotatably held at the cover plate of the device and a planetary gear meshing with the ring gear. The switch portion is formed by a moving contact, which is provided integrally with the ring gear of the planetary gear group and rotates with the ring gear, and fixed contacts, which are fixed to the cover plate and are able to contact the moving contact. The clutch mechanism has a wave washer which presses a carrier of the planetary gear due to urging force, and the clutch mechanism cuts off transmission of forward direction rotational force from the moving body (the motor output shaft) to the ring gear. In this way, when the position detecting device is used in a power window device or a sunroof device, the position of the window glass or the sunroof can be detected with high accuracy and the movement thereof can be controlled. Moreover, the initial positions can be set without complicated adjustment, and these features can be realized with a simple structure and at a low cost.
In the above-described device for detecting a position of a moving body, the parts such as the clutch mechanism (the wave washer), the ring gear, the planetary gear, and the like are sequentially installed coaxially with a predetermined axis corresponding to the moving body (the motor output shaft), with the cover plate of the device used as a reference. When assembly is completed, the carrier which supports the planetary gear is in a state of press-contacting a protective plate (immobile plate) which is fixed to the cover plate. In this way, a predetermined frictional force is applied, and rotation of the carrier (i.e., revolution of the planetary gear) is prevented, such that the moving force of the moving body is transmitted from the planetary gear to the ring gear and the ring gear is rotated.
However, the clutch force (pressing/urging force) of the clutch mechanism (the wave washer) is applied to the carrier also at the time when the planetary gear and the carrier are being provisionally installed. Therefore, when the clutch mechanism (the wave washer), the planetary gear, and the carrier are being provisionally installed with respect to the cover plate, due to the pressing/urging force of the clutch mechanism (the wave washer), the carrier and the planetary gear rise upward and the axis is shifted, which may impede precise positioning during provisional assembly and lead to a deterioration of the assemblability. Accordingly, in order to accurately install the planetary gear and the carrier coaxially with the predetermined axis with the cover plate as a reference, assembly must be carried out cautiously, and there is therefore room for improvement with respect to this point.